docs: def slug(self, language=None, fallback=True):
          """
          Return the slug of the page depending on the given language.
  
          :param language: wanted language, if not defined default is used.
          :param fallback: if ``True``, the slug will also be searched in other \
          languages.
          """
  
          slug = self.get_content(language, 'slug', language_fallback=fallback)
          if slug == '':
              return "Page {0}".format(self.pk)
  
          return slug